Structure detection in a libration vibration spectrum of water molecules by methods of nonlinear optics

In exciting water possessing an enhanced optical strength by the radiation of a YAG : Nd³⁺ laser with 20-ps pulses, nonlinear scattering of light was detected in the frequency range of the optical second harmonic. A relationship was established of the signal of the nonlinear scattering with a stimulated Raman scattering (SRS) of the laser radiation in water. Near the SRS threshold, the structure was observed in the spectrum of nonlinear scattering, which is related to intermolecular libration vibrations of water molecules.